Asked about the unprecedented growth of iPad in its first seven full quarters, Apple CEO explained at today’s Goldman Sachs keynote why he thinks the iPad has proven so popular, and been such a breakway success.

Noting that Apple has sold 55 million iPads in just seven quarters, Tim Cook noted how long it took other Apple products.

“55 million iPads shipped is something no one would have guessed, including us. It took us 22 years to sell 55 million Macs. It took 5 years to sell 55 million iPods. It took three years for us to ship that many iPhones. The trajectory is off the charts.”

But why? Tim Cook says it’s because the iPad grew organically out of everyone that came before.

“The reason the iPad is so big is because it stands on the shoulders of everything that came before it. Before iPad, the iTunes Store and App Store were already in place. People were already trained on iPhones, so they knew about multitouch. So you could literally give an iPad to anyone and there was no learning: I gave one to my mother, and she knew how to use it just by watching the commercials.”

How big can the iPad get? The sky’s the limit, because Cook believes that tablets will replace PCs for most people, just like the iPad has replaced the Mac for most of his computing.

“With the shades pulled, we started using the iPad well before it was launched,” Cook said with a laugh. “For my own personal behavior, it became obvious quickly that 80-90% of my consumption and work was done on the iPad. From the day it shipped, we believed the tablet market would become larger than the PC market, and I feel it stronger today than I did then.”

Not that Apple’s abandoning the Mac.

“I love the Mac. The Mac is still growing, and I believe it can still grow. But I strongly believe that the tablet market can beat the unit sales numbers of PCs, and do it soon.”

And what about the competition?

“Apple at the end of the day believes that people want the best product,” says Cook. “So Amazon is a different kind of competitor. Price isn’t important. No one talks about the great deal they got on a product that sucks. We love our competitors, as long as they invent their own stuff.”

We love our competitors, as long as they invent their own stuff. <– I just love this line.

Patrick mariano

We love our competitors, as long as they invent their own stuff. <– I just love this line.

FriarNurgle

Amazing sales stats in the iPad. Still don’t have one.

Terrance Shaw

Poplular.

New word!

crateish

iPad 3 will be my first. Didn’t see a place for it between my iPhone 4 and MBP until my wife got an iPad 2. Now, I get it.

C’mon, March!

saudio

Ditto…

dale2000

We’ve been Brownlee’d!

btoe83

“as long as they invent their own stuff” — I got a good kick out of that, lol!!

sarno

Dude seriously, why the hell can’t they spell check on this site. Happens ALL the time!

STRIPBLUNTS

Tim Cook is going to be a fantastic CEO for a long time!!

Munstr

We love our competitors, as long as they invent their own stuff.Is it a joke?Apple did not invented anything only repackaged.if packaging is an invention then Tim Cook is Leonardo Da Vinci.

PedroCaria

It’s a very different kind of beast, on my site medium retention time for iPhones is 14s, on iPads 1m18s…I think it’s a couch thing, I always have the bloody thing when i’m on the couch.

Dick Black

“as long as they invent their own stuff” – Funny, coming from a company that stole just as much from Xerox as Microsoft.The main reason the iPad is so popular is that it serves the masses with an interface that doesn’t require a lot of foreknowledge. Also, realistically speaking, the majority of iPad owners aren’t going to be power users.But Apple better not sit on their laurels as Windows 8 is going to prove to be a mighty competitor since it will have enterprise support and offer hardware options that Apple refuses to include.

remyngtin

amazing strategy

eyyad

LOL ditto!

Connor Mulcahey

They didn’t “steal” anything from Xerox. I’m not even going to take the time to explain why, it’s already been done like 100 times on this site.

Shepherd

What about copy? Sorry, bad pun. :-)

Shepherd

Fail

HerbalEd

What ever you want to call it ….. Apple paid Xerox with millions-of-dollars in Apple stock. It’s a fact.

About the author

John Brownlee is a Contributing Editor. He has also written for Wired, Playboy, Boing Boing, Popular Mechanics, VentureBeat, and Gizmodo. He lives in Boston with his wife and two parakeets. You can follow him here on Twitter.

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